Multilayer ceramic capacitor having internal electrodes which include nickel and antimony

ABSTRACT

A multilayer capacitor includes a body including a plurality of dielectric layers and a plurality of first and second internal electrodes alternately exposed to opposing surfaces of the body in a length direction with respective dielectric layers interposed therebetween, and first and second external electrodes disposed at opposing ends of the body in the length direction and connected to the first and second internal electrodes, respectively. The plurality of first and second internal electrodes include nickel (Ni) and antimony (Sb) or germanium (Ge).

CROSS-REFERENCE TO RELATED APPLICATION

This application is the continuation application of U.S. patentapplication Ser. No. 16/171,188 filed on Oct. 25, 2018, which claims thebenefit of priority to Korean Patent Application No. 10-2018-0041460filed on Apr. 10, 2018 in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference in theirentirety.

BACKGROUND 1. Field

The present disclosure relates to a multilayer ceramic capacitor (ormultilayer capacitor).

2. Description of Related Art

As electronic devices have tended to become more multifunctional andcompact, electronic components have been required to be miniaturized andhighly integrated.

In particular, in the case of multilayer ceramic capacitors (MLCCs)whose purposes and uses have been continuously increased asgeneral-purpose electronic components, competition for dominating themarket in advance is intense by developing ultra-high capacity productsbased on thinner dielectric layers and internal electrodes.

As the MLCCs have increasingly high capacity, the dielectric layers andinternal electrodes are reduced in thickness, which causes shortcircuits, a DC bias failure, and reliability failures.

One of the reasons for the frequent occurrence of short circuit as theinternal electrodes become thinner is electrode curling which occursduring sintering in the process of manufacturing the multilayercapacitors.

Generally, the internal electrodes are formed of nickel. Metals havecharacteristics that higher surface tension thereof makes a width of asurface thereof be reduced at high temperatures, thus changing to aspherical shape. Therefore, when the internal electrodes are sintered,the nickel internal electrodes cannot withstand a flat form at atemperature at which dielectric is sintered but are curled up (orclustered) due to the high surface tension characteristics of nickel.

In order to solve the problem of curling of the nickel internalelectrodes which causes a short-circuit failure in the multilayercapacitor, it is necessary to lower the surface tension.

SUMMARY

An aspect of the present disclosure may provide a multilayer ceramiccapacitor with improved reliability.

According to an aspect of the present disclosure, a multilayer capacitormay include: a body including a plurality of dielectric layers and aplurality of first and second internal electrodes alternately exposed toopposing surfaces of the body in a length direction with respectivedielectric layer interposed therebetween; and first and second externalelectrodes disposed at opposing ends of the body in the length directionand connected to the first and second internal electrodes, respectively.The plurality of first and second internal electrodes include nickel(Ni) and antimony (Sb).

The content of Sb in the plurality of first and second internalelectrodes may be within a range from 0.01 at % to 5 at %, based on atotal content of the first and second internal electrodes.

The content of Sb in the plurality of first and second internalelectrodes may be within a range from 0.1 at % to 1 at %, based on atotal content of the first and second internal electrodes.

The plurality of first and second internal electrodes may furtherinclude germanium (Ge).

The content of Ge in the plurality of first and second internalelectrodes may be 0.01 at % to 5 at %, based on a total content of thefirst and second internal electrodes.

The content of Ge in the plurality of first and second internalelectrodes may be within a range from 0.1 at % to 1 at %, based on atotal content of the first and second internal electrodes.

According to another aspect of the present disclosure, a multilayercapacitor may include: a body including a plurality of dielectric layersand a plurality of first and second internal electrodes alternatelyexposed to opposing surfaces of the body in a length direction withrespective dielectric layer interposed therebetween; and first andsecond external electrodes disposed at opposing ends of the body in thelength direction and connected to the first and second internalelectrodes, respectively. The plurality of first and second internalelectrodes include nickel (Ni) and germanium (Ge).

The content of Ge in the plurality of first and second internalelectrodes may be 0.01 at % to 5 at %, based on a total content of thefirst and second internal electrodes.

The content of Ge in the plurality of first and second internalelectrodes may be within a range from 0.1 at % to 1 at %, based on atotal content of the first and second internal electrodes.

The plurality of first and second internal electrodes may furtherinclude antimony (Sb).

The content of Sb in the plurality of first and second internalelectrodes may be 0.01 at % to 5 at %, based on a total content of thefirst and second internal electrodes.

The content of Sb in the plurality of first and second internalelectrodes may be within a range from 0.1 at % to 1 at %, based on atotal content of the first and second internal electrodes.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view schematically illustrating a multilayercapacitor according to an exemplary embodiment in the presentdisclosure;

FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1;

FIG. 3 is a graph illustrating surface tension of various materials;

FIG. 4 is a view illustrating elements which are completely dissolved innickel to become an alloy;

FIG. 5 is a phase diagram of Ni—Ge; and

FIG. 6 is a phase diagram of Ni—Sb.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings.

Multilayer Capacitor

FIG. 1 is a perspective view schematically illustrating a multilayercapacitor according to an exemplary embodiment in the presentdisclosure, and FIG. 2 is a cross-sectional view taken along line I-I′of FIG. 1.

Referring to FIGS. 1 and 2, a multilayer capacitor 100 according to thepresent exemplary embodiment includes a body 110 and first and secondexternal electrodes 131 and 132.

The body 110 includes an active region including a plurality ofdielectric layers 111 stacked in the Z direction and a plurality offirst and second internal electrodes 121 and 122 alternately arranged inthe Z direction with the dielectric layer 111 interposed therebetweenand cover regions disposed above and below the active region.

The body 110 is formed by stacking the plurality of dielectric layers111 and first and second internal electrodes 121 and 122 in the Zdirection and subsequently sintering the same. The body 110 is notlimited in shape and may have a substantially hexahedral shape, asillustrated.

Here, the body 110 may have first and second surfaces opposing eachother in the Z direction, third and fourth surfaces connecting the firstand second surfaces and opposing each other in the X direction, andfifth and sixth surfaces connecting the first and second surfaces,connecting the third and fourth surfaces, and opposing each other in theY direction.

The plurality of dielectric layers 111 are in a sintered state andadjacent dielectric layers 111 are integrated such that the boundarytherebetween may not be readily apparent without using a scanningelectron microscope (SEM).

Here, the thickness of the dielectric layer 111 may be arbitrarilychanged according to capacity design of the multilayer ceramic capacitor100.

The dielectric layer 111 may include a ceramic powder having a highdielectric constant, for example, a barium titanate (BaTiO₃)-based orstrontium titanate (SrTiO₃)-based powder or magnesium titanate, and thepresent disclosure is not limited thereto as long as sufficientcapacitance is obtained.

In addition, at least one of a ceramic additive, an organic solvent, aplasticizer, a binder, a dispersant, and the like, may be further addedto the dielectric layer 111 together with the ceramic powder, ifnecessary.

The cover regions, margins of the body 110 in the Z direction, areformed by arranging covers on opposing outermost sides of the body 110in the Z direction.

The covers may have the same material and configuration as those of thedielectric layer 111, except that the covers do not include an internalelectrode.

The covers may be formed by stacking a single dielectric layer or two ormore dielectric layers on the opposing outermost sides of the body 110in the Z direction, and basically serve to prevent damage to the firstand second internal electrodes 121 and 122 due to physical or chemicalstress.

The first and second external electrodes 131 and 132 may be formed of aconductive paste including a conductive metal.

The conductive metal may be, for example, nickel (Ni), copper (Cu),palladium (Pd), gold (Au), or an alloy thereof, but the presentdisclosure is not limited thereto.

The first and second external electrodes 131 and 132 may include firstand second connection portions 131 a and 132 a and first and second bandportions 131 b and 132 b.

The first and second connection portions 131 a and 132 a are disposed onthe opposing side surfaces of the body 110 in the X direction and thefirst and second band portions 131 b and 132 b extend to portions of alower surface of the body 110, i.e., a mounting surface, from the firstand second connection portions 131 a and 132 a.

Here, the first and second band parts 131 b and 132 b may further extendto at least one of portions of an upper surface of the body 110 andopposing side surfaces of the body 110 in the Y direction. Accordingly,bonding strength of the first and second external electrodes 131 and 132may be improved.

In the present exemplary embodiment, it is illustrated and describedthat the first and second band portions 131 b and 132 b of the first andsecond external electrodes 131 and 132 extend from the first and secondconnection portions 131 a and 132 a to portions of the upper surface ofthe body 110 and the opposing side surfaces of the body 110 in the Ydirection, but the present disclosure is not limited thereto.

The first and second internal electrodes 121 and 122, to which oppositepolarities are applied, are disposed in the body 110 and are disposedalternately in the Z direction with the dielectric layer 111 interposedtherebetween.

Here, the first and second internal electrodes 121 and 122 may beelectrically insulated from each other by the dielectric layer 111disposed therebetween.

Also, the first and second internal electrodes 121 and 122 includenickel (Ni) and antimony (Sb).

A small amount of Sb injected into the first and second internalelectrodes 121 and 122 allows the internal electrodes including Ni to bemore resistant to heat when sintering is performed in the process ofmanufacturing the multilayer capacitor. Thus, after the sintering,curling of the first and second internal electrodes 121 and 122 may bereduced and the first and second internal electrodes 121 and 122 may bemore flattened.

This is because Sb has low surface energy and thus is distributed on asurface of nickel when alloyed with nickel. Here, the change in thesurface characteristics is considered to better bonding between thecommon material delaying shrinkage of the internal electrodes and thesurface of nickel.

Thus, when curling of the first and second internal electrodes 121 and122 is reduced and the first and second internal electrodes 121 and 122are flattened, reliability (mean time to failure (MTTF)) of themultilayer capacitor may be improved.

Meanwhile, the first and second internal electrodes 121 and 122 mayinclude Ge.

As illustrated in FIG. 5, when a small amount of Ge is applied to Ni, Gemay be dissolved. Ge is a material having low surface tension, comparedwith nickel as illustrated in FIG. 3.

Therefore, Ge may improve reliability (MTTF) of the multilayer capacitorby acting on the internal electrodes similarly to the above-describedSb.

Table 1 shows capacity and MTTF measured after multilayer capacitorshaving length×width×thickness of 0.6×0.3×0.3 mm were manufactured byinjecting Sb or Ge into the internal electrodes.

Here, the content and distribution of Sb and Ge are detected by mappingthe internal electrodes by wavelength dispersive X-ray spectroscopy(WDX) at the cross-sections of the multilayer capacitors.

In Table 1, in sample 1, a comparative example, the internal electrodesdo not include both Sb and Ge.

TABLE 1 Metal included in Capacity MTTF # internal electrode at % (μF)(hr) 1 — 0 5.22 112 2 Sb 0.01 5.18 116 3 Sb 0.1 5.34 136 4 Sb 1 5.23 1435 Sb 5 5.02 116 6 Sb 10 4.77 88 7 Ge 0.01 5.11 120 8 Ge 0.1 5.08 125 9Ge 1 5.01 131 10 Ge 5 4.81 122 11 Ge 10 3.33 74

Referring to Table 1, it can be seen that, when the content of Sbincreases, the capacity is within a certain range, while the MTTFgradually increases, and the content of Sb decreases again from 5 at %,based on a total content of the first and second internal electrodes,and in the case of sample 6 in which the content of Sb exceeds 5 at %,the capacity is significantly lowered as compared with the comparativeexample and MTTF is also lower than that of the comparative example.

That is, in the multilayer capacitor using the internal electrodesincluding Sb of 0.01 at % to 5 at %, based on a total content of thefirst and second internal electrodes, the MTTF characteristics arerelatively improved, while realizing a capacity level similar to that ofthe comparative example.

Also, referring to Table 1, it can be seen that, when the content of Geincreases, the capacity is within a certain range, while the MTTFgradually increases, and the content of Ge decreases again from 5 at %,and in the case of sample 11 in which the content of Sb exceeds 5 at %,the capacity is significantly lowered as compared with the comparativeexample and MTTF is also lower than that of the comparative example.

That is, in the multilayer capacitor using the internal electrodesincluding Ge of 0.01 at % to 5 at %, the MTTF characteristics arerelatively improved, while realizing a capacity level similar to that ofthe comparative example.

As described above, the reason why the excellent reliability is obtainedwhen Sb or Ge is added to the internal electrodes is because Sb and Gemay be dissolved in nickel to form an alloy, and since Sb and Ge arematerials with low surface tension, they form a nickel alloy to reducesurface tension of the internal electrodes.

Referring to FIG. 3, it can be seen that Sb and Ge have significantlylower surface tension than Ni and that Sb and Ge are easily alloyed withnickel as illustrated in FIG. 4.

When Sb or Ge is alloyed to lower the surface tension, electrode curlingmay be effectively prevented when the internal electrodes are sinteredat a high temperature, and also, since a large amount of the alloyedheterogeneous elements is distributed on the surfaces of the internalelectrodes to lower the surface tension and Sb or Ge distributed on thesurfaces of the internal electrodes forms an oxide film more easily thanNi, increasing bonding force with the common material to improve thermalcontraction properties.

In Table 1, the reason why Sb exhibits MTTF better than Ge is because Sbis lower in surface tension than Ge.

Also, the content of Sb or Ge in the first and second internalelectrodes 121 and 122 exhibits excellent MTTF characteristics at 0.01at % to 5.0 at %, based on a total content of the first and secondinternal electrodes. This is because Sb or Ge is easily dissolved in Niin the content range.

FIG. 6 shows a phase diagram of Ni—Sb.

Referring to FIG. 6, it can be seen that Sb may be dissolved in Ni at amaximum of 8 at % to 9 at % at 1,100° C. and 4 at % to 5 at % at roomtemperature.

Also, research results in 1970s to 1980s regarding nickel super-alloystudies showed that Sb precipitates to the surface when Sb is added tonickel. As a result, when Sb is added to the internal electrodes, it maybe precipitated to the interface, lowering the surface tension of thealloy, improving reliability of the capacitor.

Also, as the content of Sb increases in nickel, the surface tension ofthe alloy is lowered but electrical resistance disadvantageouslyincreases.

That is, as illustrated in FIG. 6, the content of Sb is completelydissolved in Ni at room temperature up to 5 at %, based on a totalcontent of the first and second internal electrodes, and, at a highercontent, Ni₃Sb is precipitated to significantly hinder electricalconductivity.

Therefore, as illustrated in Table 1, it can be seen that when Sb isadded in an amount exceeding 5 at %, the capacity, as well as the MTTF,is lowered. It is also confirmed that the characteristics are improvedeven when the amount of Sb is 0.01 at %.

That is, in the present composition, a content of Sb may be within arange from 0.01 at % to 5.0 at %, based on a total content of the firstand second internal electrodes.

When the internal electrodes of the multilayer capacitor are formed bythe paste including Ni and Sb, surface tension of the internalelectrodes may be lowered, and when Sb is alloyed, Sb is precipitated tothe surface, lowering interface potential and resistance with adielectric layer to improve reliability of the multilayer capacitor.

As set forth above, according to exemplary embodiments of the presentdisclosure, the internal electrodes are formed of a paste including Niand Sb to lower surface tension of the internal electrodes, and when Sbis alloyed, Sb is precipitated to the surface, lowering interfacepotential and resistance with a dielectric layer to improve reliabilityof the multilayer capacitor.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentdisclosure as defined by the appended claims.

What is claimed is:
 1. A multilayer capacitor comprising: a bodyincluding a plurality of dielectric layers and a plurality of first andsecond internal electrodes alternately exposed to opposing surfaces ofthe body in a length direction with respective dielectric layersinterposed therebetween, wherein the plurality of first and secondinternal electrodes include nickel (Ni) and antimony (Sb), and a contentof Sb in the plurality of first and second internal electrodes is withina range from 0.01 at % to 5 at %, based on a total content of the firstand second internal electrodes.
 2. The multilayer capacitor of claim 1,wherein the content of Sb in the plurality of first and second internalelectrodes is within a range from 0.1 at % to 1 at %, based on the totalcontent of the first and second internal electrodes.
 3. The multilayercapacitor of claim 1, wherein the plurality of first and second internalelectrodes further include germanium (Ge).
 4. The multilayer capacitorof claim 3, wherein a content of Ge in the plurality of first and secondinternal electrodes is within a range from 0.01 at % to 5 at %, based ona total content of the first and second internal electrodes.
 5. Themultilayer capacitor of claim 4, wherein the content of Ge in theplurality of first and second internal electrodes is within a range from0.1 at % to 1 at %, based on the total content of the first and secondinternal electrodes.
 6. A multilayer capacitor comprising: a bodyincluding a plurality of dielectric layers and a plurality of first andsecond internal electrodes alternately exposed to opposing surfaces ofthe body in a length direction with respective dielectric layersinterposed therebetween, wherein the plurality of first and secondinternal electrodes include antimony (Sb), nickel (Ni) and germanium(Ge), and a content of Sb in the plurality of first and second internalelectrodes is within a range from 0.1 at % to 1 at %, based on a totalcontent of the first and second internal electrodes.
 7. The multilayercapacitor of claim 6, wherein a content of Ge in the plurality of firstand second internal electrodes is within a range from 0.01 at % to 5 at%, based on a total content of the first and second internal electrodes.8. The multilayer capacitor of claim 7, wherein the content of Ge in theplurality of first and second internal electrodes is within a range from0.1 at % to 1 at %, based on the total content of the first and secondinternal electrodes.